1. Field of the Invention
The present invention relates to a method and apparatus for smelting iron oxide or more particularly for melting prereduced iron oxide generally in the form of wustite, in a natural gas/oxygen bottom blown melting vessel which incorporates a hot air blast above the bath for post combustion of off gases.
2. Description of the Prior Art
In the presently operated smelting reduction processes, coal is utilized as the fuel. Coal is injected into the bath or blown onto the top of the bath but is not combusted with oxygen. Coal, or other fuel, is always introduced into the smelter as a separate process stream and not with any other reactant or component.
In addition, in presently operated processes, iron oxide is introduced to smelting reduction furnaces in the agglomerated forms of pellets or briquets to minimize creation and emission of dust from the smelter, which dust adheres to the interior walls of smelter off-gas ducts or conduits, clogging these gas passageways.
The applicants are aware of the following patents concerning iron oxide smelting and related matters, which vary in relevance to the present invention. The patent number refers to a U.S. Patent Number unless indicated otherwise.
__________________________________________________________________________ Pat. No. Issue Date Inventor Title __________________________________________________________________________ 4,195,985 Apr. 1, 1980 BROTZMANN METHOD OF IMPROVEMENT OF THE HEAT-BALANCE IN THE REFINING OF STEEL EURO 017 963 Oct. 29, 1980 HIRAL, et al CONVERTER STEELMAKING PROCESS 3,960,546 Jun. 1, 1976 ROTE et al METHOD FOR ELIMINATING NOSE- SKULLS FROM STEELMAKING VESSELS 4,029,497 Jun. 14, 1977 NIXON MANUFACTURE OF ALLOY STEELS AND FERROUS ALLOYS 4,543,123 Sep. 24, 1985 VULETIC PROCESS FOR THE DIRECT PRODUCTION OF SPONGE IRON PARTICLES AND LIQUID CRUDE IRON FROM IRON ORE IN LUMP FORM 2,757,921 Aug. 7, 1956 PETERSON METHOD FOR BURNING OF MATERIALS WITH HEAT RECOVERY 3,776,533 Dec. 4, 1973 VLNATY APPARATUS FOR CONTINUOUS HEAT PROCESSING OF ORE PELLETS 4,712,774 Dec. 15, 1987 LOUIS DEVICE FOR THE MELTING OF LIGHT METALS 4,715,584 Dec. 29, 1987 HENGELMOLEN FURNACE FOR MELTING METALS 4,212,452 Jul. 15, 1930 HSIEH APPARATUS FOR THE DIRECT REDUCTION OF IRON ORE 4,397,684 Aug. 9, 1983 GROSJEAN PROCESS FOR PNEUMATIC STIRRING OF A BATH OF MOLTEN METAL 4,356,035 Oct. 26, 1982 BROTZMANN et al STEELMAKING PROCESS 4,272,287 Jun. 9, 1981 YAJIMA et al PROCESS FOR REFINING MOLTEN STEEL CONTAINING CHROMIUM 4,409,024 Oct. 11, 1983 KATO TOP-AND-BOTTOM BLOWN CONVERTER STEELMAKING PROCESS 3,854,932 Dec. 17, 1974 BISHOP, JR. PROCESS FOR PRODUCTION OF STAINLESS STEEL 4,302,244 Nov. 24, 1981 SIECKMAN et al STEEL CONVERSION METHOD 4,592,778 Jun. 3, 1986 FUJII et al STEELMAKING OF AN EXTREMELY LOW CARBON STEEL IN A CONVERTER 4,280,838 Jul. 28, 1981 MARUKAWA et al PRODUCTION OF CARBON STEEL AND LOW-ALLOY STEEL WITH BOTTOM BLOWING BASIC OXYGEN FURNACE 4,290,802 Sep. 22, 1981 HIRATA et al STEEL MAKING PROCESS 4,334,921 Jun. 15, 1982 HIRAI et al CONVERTER STEELMAKING PROCESS 4,358,314 Nov. 9, 1982 NORMANTON METAL REFINING PROCESS 4,402,739 Sep. 6, 1983 NAKANISHI et al METHOD OF OPERATION OF A TOP-AND-BOTTOM BLOWN CONVERTER 4,651,976 Mar. 24, 1987 ARIMA et al METHOD FOR OPERATING A CONVERTER USED FOR STEEL REFINING UK 2059997A Apr. 29, 1981 BOGDANDY et al METHOD OF MAKING STEEL FROM SOLID FERROUS METAL CHARGES EURO 111 176 Nov. 11, 1983 KORF et al METHOD AND INSTALLA- TION FOR DIRECT PRODUCTION OF SPONGE IRON PARTICLES 4,008,074 Feb. 15, 1977 ROSSNER et al METHOD FOR MELTING SPONGE IRON __________________________________________________________________________
Brotzmann U.S. Pat. No. 4,195,985 teaches both top and bottom blowing, with an improved heat balance. This reference discloses after-burning of the carbon monoxide, and also discloses the use of natural gas, but not as the sole fuel.
European Patent Application No. 17,963 of Nippon Steel teaches a top and bottom blown smelting operation, and sets forth a thorough description of the prior art.
The Rote patent teaches the use of combustible fuel such as natural gas, propane, fuel oil or the like (see column 3, lines 5 to 7). Rote's top and bottom blown vessel is concerned with reducing nose skull in the top of the vessel, and utilizes commercially pure oxygen.
Nixon teaches that wustite can be treated by blowing it with a feed gas which is reducing to wustite in a converter.
Vuletic shows removal of large particulates, so they will not reach the fluidized bed. Rossner shows a similar process, but omits the natural gas and the top air elements.
With the exception of Rote, the patents cited above do not appear to show any teaching of one-hundred percent (100%) of the fuel being natural gas, nor do any of them specifically show air rather than substantially pure oxygen as the combustion gas above the bath.
Applicants are unaware of any prior art that accomplishes the objects of the present invention. Consequently, a need exists for a method and apparatus which will result in improved smelting of iron oxide, particularly from the form of wustite.